A counter contains several advanced terminals that you can use to perform time measurements and generate pulses. For most applications, NI-DAQmx automatically makes the proper routes from the terminal connector block to the correct advanced terminal with no additional routing required. For advanced applications, you might need to make explicit routes to the internal counter terminals

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Advanced Terminals and Common Counter Applications

The following list identifies the names of the advanced terminals as well as their common uses:

CtrnGate—The signal at this advanced terminal is used as the Start Trigger, pause trigger, sample clock, or the input signal being measured. The following table lists how this terminal is used in various applications:

Application

Purpose of Gate Terminal

Pulse Generation

Pause or Start Trigger

One Counter Time Measurements

Input Signal

Two Counter Time Measurements

Unused

Nonbuffered Edge Counting

Pause Trigger

Buffered Edge Counting

Sample Clock

Two-Edge Separation

Second Input Terminal

Position

Z Input Terminal

CtrnSource—The signal at this advanced terminal is either the input terminal for the measurement or the counter timebase. The following table lists how this terminal is used in various applications:

Application

Purpose of Source Terminal

Pulse Generation

Counter Timebase

One Counter Time Measurements

Counter Timebase

Two Counter Time Measurements

Input Terminal

Nonbuffered Edge Counting

Input Terminal

Buffered Edge Counting

Input Terminal

Two-Edge Separation

Counter Timebase

Position

A Input Terminal

CtrnInternalOutput—The signal at this advanced terminal is where the pulsed or toggled output of the counter appears. The output of a counter pulses or toggles when the counter reaches terminal count. When counting down, the counter reaches terminal count when the count reaches zero. When counting up, the counter reaches terminal count when the counter rolls over. To configure the counter to toggle or generate pulses, use the Export Signal function/VI with Counter Output Event as the signal name.

For the output of a counter to appear at the I/O connector (Ctr0Out, for example), the signal on the internal output terminal must be routed to a terminal on the I/O connector. For pulse generations, this route is automatically made to the dedicated counter output terminal on the I/O connector. For measurements, if you are interested in observing this signal, you need to manually make this route to the appropriate pin on the I/O connector using the Export Signal function/VI with Counter Output Event as the signal name. After you route the internal output of a counter to the I/O connector, the signal remains on the I/O connector until the device is reset or you explicitly tristate the terminal.

CtrnAux—The following table lists how this terminal is used in various applications:

Application

Purpose of Aux Terminal

Pulse Generation

Unused

One Counter Time Measurements

Unused

Two Counter Time Measurements

Unused

Nonbuffered Edge Counting

Optional Count Direction Terminal

Buffered Edge Counting

Optional Count Direction Terminal

Two-Edge Separation

First Input Terminal

Position

B Input Terminal

CtrnSampleClock—You can connect a sample clock in or export it through this terminal.

Counter Parts

The main parts of a counter include the following:

A GATE input terminal controls when counting occurs. A GATE input is similar to a trigger because it starts or stops a count.

A SOURCE (CLK) input terminal is the timebase for a measurement or the signal to count.

A count register increments or decrements the number of edges to count. If the count register decrements, it counts down to zero. The count register size is the number of bits in the counter, and you calculate it as Count Register = 2no. of bits.

An OUT signal terminal can output a pulse or a pulse train, which is a series of pulses.

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